Minimally-invasive heart valves and methods of use

ABSTRACT

Expandable heart valves for minimally invasive valve replacement surgeries are disclosed. In a first embodiment, an expandable pre-assembled heart valve includes a plastically-expandable annular base having plurality of upstanding commissure posts. A tubular flexible member including a prosthetic section and a fabric section is provided, with the prosthetic section being connected to the commissure posts and defining leaflets therebetween, and the fabric section being attached to the annular base. In a second embodiment, an expandable heart valve includes an annular tissue-engaging base and a subassembly having an elastic wireform and a plurality of leaflets connected thereto. The annular base and subassembly are separately stored and connected just prior to delivery to the host annulus. Preferably, the leaflet subassembly is stored in its relaxed configuration to avoid deformation of the leaflets. The expandable heart valves may be implanted using a balloon catheter. Preferably, the leaflets of the heart valves are secured to the commissure regions of the expandable stents using a clamping arrangement to reduce stress.

FIELD OF THE INVENTION

The present invention relates generally to medical devices andparticularly to expandable heart valve prostheses especially for use inminimally-invasive surgeries.

BACKGROUND OF THE INVENTION

Prosthetic heart valves are used to replace damaged or diseased heartvalves. In vertebrate animals, the heart is a hollow muscular organhaving four pumping chambers: the left and right atria and the left andright ventricles, each provided with its own one-way valve. The naturalheart valves are identified as the aortic, mitral (or bicuspid),tricuspid and pulmonary valves. Prosthetic heart valves can be used toreplace any of these naturally occurring valves, although repair orreplacement of the aortic or mitral valves is most common because theyreside in the left side of the heart where pressures are the greatest.

Where replacement of a heart valve is indicated, the dysfunctional valveis typically cut out and replaced with either a mechanical valve, or atissue valve. Tissue valves are often preferred over mechanical valvesbecause they typically do not require long-term treatment withanticoagulants. The most common tissue valves are constructed with wholeporcine (pig) valves, or with separate leaflets cut from bovine (cow)pericardium. Although so-called stentless valves, comprising a sectionof porcine aorta along with the valve, are available, the most widelyused valves include some form of stent or synthetic leaflet support.Typically, a wireform having alternating arcuate cusps and upstandingcommissures supports the leaflets within the valve, in combination withan annular stent and a sewing ring. The alternating cusps andcommissures mimic the natural contour of leaflet attachment.Importantly, the wireform provides continuous support for each leafletalong the cusp region so as to better simulate the natural supportstructure.

A conventional heart valve replacement surgery involves accessing theheart in the patient's thoracic cavity through a longitudinal incisionin the chest. For example, a median sternotomy requires cutting throughthe sternum and forcing the two opposing halves of the rib cage to bespread apart, allowing access to the thoracic cavity and heart within.The patient is then placed on cardiopulmonary bypass which involvesstopping the heart to permit access to the internal chambers. Such openheart surgery is particularly invasive and involves a lengthy anddifficult recovery period.

Recently, a great amount of research has been done to reduce the traumaand risk associated with conventional open heart valve replacementsurgery. In particular, the field of minimally invasive surgery (MIS)has exploded since the early to mid-1990s, with devices now beingavailable to enable valve replacements without opening the chest cavity.MIS heart valve replacement surgery still requires bypass, but theexcision of the native valve and implantation of the prosthetic valveare accomplished via elongated tubes or cannulas, with the help ofendoscopes and other such visualization techniques.

Some examples of MIS heart valves are shown in U.S. Pat. No. 5,980,570to Simpson, U S. Pat. No. 5,984,959 to Robertson, et al., and PCTPublication No. WO 99/334142 to Vesely. Although these and other suchdevices provide various ways for collapsing, delivering, and thenexpanding a “heart valve” per se, none of them disclose an optimumstructure for tissue valves. For instance, the publication to Veselyshows a tissue leaflet structure of the prior art in FIG. 1, and anexpandable inner frame of the invention having stent posts in FIGS.3A-3C. The leaflets are “mounted to the stent posts 22 in a mannersimilar to that shown in FIG. 1.” Such a general disclosure stops shortof explaining how to construct an optimum valve. In particular, themeans of attaching the leaflets to the MIS stent is critical to ensurethe integrity and durability of the valve once implanted. All of theprior art MIS valves fall short in this regard.

In view of the foregoing, it is evident that an improved sewing ringthat addresses the apparent deficiencies in existing expandable heartvalves is necessary and desired.

SUMMARY OF THE INVENTION

The present invention provides an expandable prosthetic heart valve forplacement in a host heart valve annulus, comprising an expandable stentsystem adapted to be delivered in a collapsed state to an implantationsite and expanded, and a plurality of prosthetic leaflets attached tothe stent system. Each leaflet has an approximately semi-circular cuspedge terminating at each end in commissure portions, and a coapting edgeextending between the commissure portions. Each leaflet is attached tothe stent system substantially entirely along the cusp edge and at bothcommissure portions, with a coapting edge remaining unattached. Thestent system may comprise an expandable generally annulartissue-engaging base and an elastic generally annular wireform attachedthereto. The base is adapted to be delivered in a radially collapsedstate and expanded into contact with the host annulus. The annularwireform defines a plurality of upstanding commissures and a pluralityof arcuate cusps between adjacent commissures, and the prostheticleaflets are attached to the wireform along the cusps and commissures,wherein the wireform and leaflets are configured to be radiallycompressed.

In one embodiment, the heart valve includes a plurality of upstandingposts attached to one of the tissue-engaging base and elastic wireform,each post having a connector. A plurality of mating connectors areprovided on the other of the tissue-engaging base and elastic wireformfor mating with the post connectors. The posts and mating connectors maybe provided for each commissure and each cusp of the elastic wireform sothat the valve includes a number of posts and mating connectors equal tothe number of commissures plus the number of cusps. Further, theexpandable stent system may include an undulating wireform defining aplurality of commissures and a plurality of cusps between adjacentcommissures. The cusp edge of each of the prosthetic leaflets attachesalong a wireform cusp, and the commissure portions of each leafletterminate in outwardly extending tabs that each attach to a wireformcommissure, wherein tabs from adjacent leaflets are attached together ateach of the wireform commissures.

In another aspect of the invention, an expandable prosthetic heart valvefor placement in a host heart valve annulus is provided. The heart valvecomprises an expandable stent portion and an elastic leaflet portionconnectable to the stent portion. The stent portion defines an inflowend of the valve and is adapted to be delivered in a collapsed state andexpanded into contact with the host annulus. The leaflet portion forms aone-way flow occluder on an outflow end of the valve and includes anelastic wireform defining alternating cusps and commissures andprosthetic tissue attached substantially entirely therealong. The stentportion desirably includes a tubular member and a plurality ofconnectors, and wherein a plurality of connectors are provided on theelastic wireform for mating with the tubular member connectors. Thewireform connectors may be provided on each commissure and on each cuspof the wireform so that the valve includes a number of mating connectorsequal to the number of commissures plus the number of cusps. In apreferred embodiment, the prosthetic tissue comprises a plurality ofindividual leaflets secured along the alternating cusps and commissuresof the elastic wireform. Additionally, the wireform may have a fabriccovering, wherein the individual leaflets are stitched along the fabriccovering. The fabric covering continues toward an inflow end of thevalve in a skirt that surrounds the stent portion and is adapted to becaptured between the expanded stent portion and the host annulus. Aplurality of posts rigidly may connect to the stent portion and extendupward within the skirt into mating connection with the elasticwireform.

In a still further aspect, the present invention provides a two-partexpandable prosthetic heart valve for placement in a host heart valveannulus, comprising:

a leaflet subassembly having a wireform defining a plurality ofupstanding commissures and a plurality of arcuate cusps extendingbetween adjacent commissures, a midpoint of each cusp being locatedapproximately equidistant from the adjacent commissures;

a generally annular tissue-engaging base defining an axis; and

a system for connecting the leaflet subassembly and the tissue-engagingbase, including a plurality of mating connectors on the leafletsubassembly and on the tissue-engaging base, wherein one connector eachis provided at each commissure, and one at each cusp midpoint.

In the two-part heart valve, the tissue-engaging base preferablycomprises an expandable tubular member that is deliverable to the hostannulus in a collapsed state and expandable into contact with the hostannulus to secure the valve therein. Furthermore, the tissue-engagingbase forms an inflow end of the valve, and the system for connecting theleaflet subassembly and tissue-engaging base includes a plurality ofposts coupled to the tubular member and having varying lengths extendingaway from the inflow end of the valve. A first plurality of posts eachhaving a first length connects with the wireform commissures, and asecond plurality of posts each having a second length connects with thewireform cusps shorter than the first length. The mating connectors maybe configured to be joined together by axial compression, preferablywith a snap-fit configuration.

A further aspect of the invention includes a prosthetic heart valvehaving a support stent and a flexible tubular member. The support stentincludes a tubular base along an inflow end a plurality of generallyaxially-extending commissure posts disposed evenly around the tubularbase on an outflow end thereof. The flexible tubular member has aprosthetic section attached to the commissure posts so as to define aplurality of the prosthetic valve leaflets between the posts, and afabric section connected to the base. The prosthetic section and fabricsection are desirably both generally tubular and attached together at aseam, wherein the seam is spaced from the outflow end of the tubularbase so that only the fabric section of the flexible tubular membercontacts the tubular base. The commissure posts each may have an axialslot, wherein the tubular member is primarily located within the postsexcept for a plurality of loops that extend outward through each slot oneach post. A plurality of inserts sized larger than the slots may beprovided, each of which insert is captured within a loop extendingoutward through each slot to retain the loop through the slot. In apreferred embodiment, the commissure posts are integrally formed withthe base, the base and commissure posts being initially formed from aflat section of material, wherein the commissure posts initially extendfrom the inflow end of the base and are bent 180° to extend alongsidethe base and project beyond the base at the outflow end thereof.

A prosthetic heart valve of the present invention has a support stentincluding a tubular base along an inflow end. A plurality of generallyaxially-extending commissure posts each having an axial slot is disposedevenly around the tubular base on an outflow end thereof. A flexibletubular member having an outflow edge is primarily located within theposts except for a plurality of loops that extend outward through eachslot on each post. Further, a plurality of inserts sized larger than theslots are provided, each of which insert is captured within a loopextending outward through each slot to retain the loop through the slot,the outflow edge of the tubular member defining a plurality of valveleaflets. The tubular base may be plastically-expandable from a firstsize adapted for minimally invasive delivery, to a second, functionalsize that fits within a heart valve annulus.

A method of minimally-invasive heart valve replacement surgery on apatient is also provided by the present invention. The method includesthe steps of:

providing an annular tissue-engaging base, the base being expandablefrom a collapsed state;

providing a generally annular elastic wireform subassembly having aplurality of prosthetic leaflets connected thereto, the elastic wireformsubassembly having a relaxed, expanded size and a compressed, reducedsize;

connecting the wireform and leaflets to the base to form a heart valve;

delivering the heart valve with the connected base in its collapsedstate and wireform subassembly in its reduced size to an annulus of thepatient's heart valve being replaced; and

expanding the base into its expanded state in contact with the annulus.

The step of delivering the heart valve to the annulus may beaccomplished by passing the valve through the patient's vasculature orvia a minimally-invasive port in the patient's chest. Thetissue-engaging base may plastically-expandable from its collapsed stateto its expanded state, and the step of expanding theplastically-expandable base comprises inflating a balloon within theannular base.

A further understanding of the nature and advantages of the inventionwill become apparent by reference to the remaining portions of thespecification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a first embodiment of anexpandable heart valve of the present invention, including a supportstent and a flexible tubular member;

FIG. 2 is an assembled perspective view of the expandable heart valve ofFIG. 1;

FIG. 3 is a longitudinal cross-sectional view taken along line 3—3through a commissure of the expandable heart valve of FIG. 2;

FIG. 4 is a transverse cross-sectional view taken along line 4—4 throughthe commissure of the expandable heart valve of FIG. 2;

FIG. 5 is a top plan view of the expandable heart valve of FIG. 2;

FIG. 6 is an exploded perspective view of a second embodiment of anexpandable heart valve of present invention having two detachablecomponents designed to be assembled post-storage, including atissue-engaging base and a wireform-supported leaflet subassembly;

FIG. 7 is an assembled perspective view of the expandable heart valve ofFIG. 6, with a fabric skirt removed to illustrate details of aconnecting system between the base and leaflet subassembly;

FIG. 8 is a plan view of an insert used to both attach individualleaflets to commissures of the wireform, and connect the commissures ofthe leaflet subassembly to the tissue-engaging base of the expandableheart valve of FIG. 6;

FIG. 9 is a plan view of an individual leaflet for use in the expandableheart valve of FIG. 6;

FIG. 10 is a longitudinal cross-sectional view taken along line 10—10 ofFIG. 7;

FIG. 11 is a transverse cross-sectional view taken along line 11—11 ofFIG. 7;

FIG. 12 is a longitudinal cross-sectional view taken along line 12—12 ofFIG. 7;

FIG. 13 is a top plan view of the expandable heart valve taken alongline 13—13 of FIG. 7;

FIG. 14 is an enlarged perspective view of a commissure region of theexpandable heart valve taken within the circle 14 of FIG. 7;

FIG. 15 is an enlarged plan view of the commissure region of theexpandable heart valve taken within the circle 15 of FIG. 13; and

FIGS. 16A-C illustrate a heart in section and several steps in adelivery and implantation procedure of the expandable valve of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention discloses two different expandable heart valvesfor implantation in a host annulus, or host tissue adjacent the annulus.The valves may be implanted in any of the four valve positions withinthe heart, but are more likely to be used in replacing the aortic valvebecause of the circular shape of the annulus.

It should also be noted that the specific constructional details,including materials and shapes, may be varied from those shown. Forexample, an expandable tubular base is used in both valve embodiments,and is described as being a plastically-expandable structure thatradially expands into contact with the annulus tissue. Alternatively,the tubular base may be elastically- or self-expandable, or expandableon the application of heat (i.e., using shape memory material). Further,various means are known for plastically or elastically expandingstructures into contact with anatomical passageways, and though thepresent invention illustrates and describes only one such structure,others may be used to practice the invention. For example, anyplastically- or elastically-expandable structure may be modified so asto have a suitable diameter for heart valves and used to practice thepresent invention. In addition, barbs, flanges, staples, and the likemay be added to the tubular base for the purpose of greater attachmentto the host tissue. In short, the present invention should not beconstrued to be limited to the particular structures and materialsdisclosed, the scope of the invention being solely defined by theappended claims.

With reference to FIGS. 1-5, a first embodiment of an expandableprosthetic heart valve 20 is shown and described. The prosthetic heartvalve 20 is assembled prior to storage. In a second embodiment, shown inFIGS. 6-15, a second embodiment of an expandable heart valve is shownand described. Detachable components of the expandable heart valve inthe second embodiment are separately stored, and assembled just prior toinsertion and delivery to the host annulus, which provides certainadvantages to be described.

Pre-Assembled Expandable Heart Valve

FIG. 1 illustrates the first embodiment of the expandable heart valve 20exploded, with a flexible tubular member 22 separated from a supportstent 24 along a central axis 26. FIG. 2 illustrates the flexibletubular member 22 attached to the support stent 24 to form the assembledheart valve 20. The heart valve 20 has an inflow end 28 (the lower endin the figure) and an outflow end 30 (the upper end in the figure).

The flexible tubular member 22 comprises a leaflet section 32 connectedto a fabric section 34 at a seam 36. As illustrated, both the leafletsection 32 and fabric section 34 are desirably formed as tubes, suchthat the seam 36 defines a circle therebetween. Alternatively, the seam36 may be other than circular if areas of the leaflet section 32 orfabric section 34 need to be expanded around their circumferentialjuncture. For example, the fabric section 34 may need to be increased inthe commissure region of the valve 20, such as indicated by the dashedline 38 in FIG. 1. Whatever the configuration, the fabric section 34 hasa minimum axial height indicated at A.

Desirably, the leaflet section 32 is formed from pericardial tissue,such as bovine or equine pericardium, suitably treated to render itbiocompatible. Of course, any suitable leaflet material, includingsynthetics, may be used. The fabric section 34 is desirably a wovenpolyester, such as polyethylene terepthalate. Alternatively, the fabricsection 34 may be formed of polytetrafluoroethylene (PTFE), or othersuitable biocompatible sheet material. Still further, the leafletsection 32 may extend the entire axial height of the flexible tubularmember 22, with the fabric section 34 being wrapped around and attachedto the inflow end.

As seen in FIG. 1, the support stent 24 comprises a tubular base 40 anda plurality of upstanding commissure posts 42 distributed evenly aroundthe periphery thereof. That is, the tubular base 40 is provided at theinflow end 28 of the support stent 24, with the commissure posts 42extending in the outflow direction. Desirably, there are three suchcommissure posts 42 disposed at 120° intervals about the circumferenceof the stent 24. The tubular base 40 has an axial height indicated at B,which height is less than the axial height A of the fabric section 34 ofthe flexible tubular member 22. The commissure posts 42 extending upwarda sufficient distance such that the entire axial dimension of thesupport stent 24 is slightly greater than the axial dimension of theflexible tubular member 22, as indicated in the assembled view of FIG.2.

The tubular base 40 comprises a plastically-expandable material that canbe expanded into the configuration shown in the figures from a radiallycompressed configuration (not shown). In this regard, the illustratedtubular base 40 essentially comprises a non-self expanding stent thatcan be expanded from its compressed state using a balloon inflated fromwithin the base, for example. Numerous configurations of suchplastically-expandable tubes are available in the prior art, and asmentioned above, the present invention should not be considered limitedto any one configuration. Moreover, in other configurations the base 40may be self- or heat-expandable.

With reference to FIG. 1, each commissure post 42 attaches to or extendsfrom an inflow rim 44 of the tubular base 40, continuing on the outsideof the tubular base toward the outflow end in an elongatedaxially-extending lower section 46, and terminating in an axiallyextending upper section 48. The upper section 48 commences at apredetermined distance above an outflow rim 50 of the tubular base 40and is stepped radially inward from the lower section 46 at a transitionregion 52. An axial slot 54 is provided in the upper section 48 and inthe transition region 52. The width of the axial slot 54 is desirablyconstant in the upper section 48, but increases at a relief region 56 inthe transition region 52.

In a preferred embodiment, the commissure posts 42 are formed of abiocompatible, elastic material, preferably metallic. For example, eachcommissure post 42 may be formed of stainless-steel, titanium, orElgiloy. Alternatively, the commissure posts 42 may be a biocompatiblepolymer, such as Delrin or polyacetyl.

In a preferred embodiment, the support stent 24 is formed from a singlepiece of flat material. Specifically, the tubular base 40 initiallycomprises a flat, narrow strip of uniform width material with thecommissure posts 42 extending from one long side thereof. Usingconventional means, the narrow strip of material is then rolled into thetubular shape shown in the figures, and the juxtaposed narrow endsjoined by, for example, crimping. Each of the commissure posts 42 isthen bent 180° outward to project in the opposite direction from theiroriginal direction. FIG. 1 illustrates such a configuration in which a180° bend 60 joins each commissure post 42 to the inflow rim 44. Theradius of the bend 60 is such that a narrow space 62 is defined betweenthe lower section 46 of each commissure post 42 and the exterior of thetubular base 40.

The flexible tubular member 22 attaches to the support stent 24 as seenin FIG. 2,with the leaflet section 32 connected to the commissure posts42, and the fabric section 34 connected to the tubular base 40. Morespecifically, the fabric section 34 surrounds the tubular base 40 andextends toward the inflow rim 44 in the spaces 62 created inboard ofeach commissure post 42. Although not shown, the fabric section 34 maybe attached to the exterior of the tubular base 40, such as by suturespassed through the fabric and through openings in the tubular base.Because the axial dimension A of the fabric section 34 is greater thanthe axial dimension B of the tubular base 40, the seam 36 is disposedabove the outflow rim 50 (FIG. 1) of the base. This is more clearlyshown in the cross-section of FIG. 3.

The leaflet section 32 is disposed substantially between the commissureposts 42, except for a number of loops 70 threaded outward through theaxial slots 54. As seen FIGS. 2-3, the loops 70 comprises regions of thetubular leaflet section 32 pinched and threaded through the axial slots54. A plurality of inserts 72 are used to secure the loops 70 to theexterior of the commissure posts 42. That is, as seen FIG. 4, theinserts 72 each have a width W that is greater than the circumferentialwidth of the axial slots, 54. Because the inserts 72 are disposed withinthe loops 70, they prevent the loops from pulling inward again throughthe axial slot 54. A plurality of stitches 74 are preferably provided tosecure the leaflet section 32 to the inserts 72. In addition, as seen inFIG. 3, stitching 76 passes through an aperture 78 in each insert 72,and through an aperture 80 provided in the outflow end of eachcommissure post 42. In this manner, each insert 72 is secured withrespect to the support stent 24.

With reference to FIGS. 2 and 5, a plurality of leaflets 82, are definedbetween the support stents 24 by the leaflet section 32. Specifically,where there are three stent post 24, a generally triangular arrangementof leaflets 82 remains unconstrained in the middle portion of the valve20 and opens and closes depending on blood flow forces. Furthermore, thecontinuous flexible tubular member 22 provides a flow channel for bloodthrough the valve 20. When the pressure differential is such that bloodflows into the inflow end 28 of the valve 20, the leaflets 82 spreadapart and the valve opens. Conversely, when the pressure differentialreverses, the leaflets 82 come together, or coapt, to close the valve20.

When the pressures are such that the valve closes, radially inwardforces are imposed on the free edge of the leaflet section 32, which maytend to cantilever the support stents 24 inward a slight amount.Localized stresses on the leaflet section 32 are reduced at theconnection with the stent supports 24, however, because of the use ofthe inserts 72 within the loops 70. That is, as best seen in FIG. 4,radially inward forces on the leaflets 82 as indicated by the arrow 84,pull the inserts 72 inward such that the leaflet material is clampedbetween each insert and the respective commissure post 42. Althoughstitching 74 through the leaflet section 32 is provided, such stitchingis not subjected to direct tensile stresses, and thus is less likely totear through the leaflet tissue.

Certain features of the valve 20 reduce wear typically associated withstent-leaflet dynamic contact. First, because the axial dimension A ofthe fabric section 34 is greater than the dimension B of the tubularbase 40, any contact between the flexible tubular member 22 and thetubular base 40 (at the outflow rim 50) is between fabric and the base.That is, the leaflet section 32 is not placed in contact with the base40, thus increasing the life of the valve. Additionally, the enlargedrelief region 56 of the slot 54 in the transition region 52 helps reducethe rubbing that might otherwise occur between the commissure posts 42and the leaflets 80. That is, the leaflet section 32 continuessubstantially axially downward from the loops 70, as seen in FIG. 3, andthe relief region 56 provides a small gap in the transition region 52between the leaflet tissue and the sides of the slot 54 to help preventrubbing therebetween.

In use, the assembled heart valve 20 as seen in FIG. 2 is initiallyprovided in a radially compacted configuration (not shown). Preferably,the valve 20 is loaded about a balloon catheter and within a deliverycannula. The balloon catheter with the valve 20 loaded thereon is thanpassed through the patient's vasculature (or through an access port inthe chest) into proximity with the host annulus. Alternatively, wherethe chest of the patient is opened, the reduced size valve 20 isinserted into position using a holder.

Once in position within the annulus of the valve being replaced, theballoon (or other expanding means) causes the tubular base 40 to expandinto contact with the annulus. Actually, because the commissure posts 42and fabric section 34 surround tubular base 40, these elements arecompressed against the host annulus. Because the tubular base 40 isplastically-expandable, it substantially retains its expanded shape. Aslight over-expansion of the tubular base 40 may be required tocompensate for any elastic spring-back character of the material used.Again, barbs or staples may also be utilized to further secure the valve20 and in place. Ultimately, the balloon catheter is deflated andremoved from within the valve 20.

Expandable Heart Valve Assembled Post-Storage

FIGS. 6-15 illustrate an expandable prosthetic heart valve 100including, as best seen in FIG. 6, a leaflet subassembly 102 adapted toconnect to a tissue-engaging base 104. The two components are both shownin FIG. 6 in their radially expanded configurations, though both aredesigned to be radially compressed and delivered through a catheter orcannula, for example. In contrast with the first embodiment, however,the two components are stored separately, and connected just prior todelivery into the body of the patient. In general, the two componentsprovide a tissue-engagement ring and a relatively more flexible valvemember having fluid occluding surfaces. It should be understood thatconfigurations of these two connectable components other than thosespecifically shown may be encompassed by the appended claims.

As seen in FIG. 6, the leaflet subassembly 102 comprises an elasticwireform 106 supporting a plurality of prosthetic leaflets 108, and afabric skirt 110. The wireform 106 comprises a continuous undulatingpattern of alternating commissures 112 and cusps 114. Preferably, thevalve 100 is a tri-leaflet type, such that the wireform 106 has threecommissures 112 and three cusps 114, with three leaflets 108 supportthereby. In particular, each leaflet 108 is desirably attached toadjacent commissures 112, and along the entire arcuate cusp 114therebetween. As will be described in more detail below, the leaflets108 each attach to a fabric covering 1 16 around the wireform cusps 114.In a preferred embodiment, the elastic wireform 106 is formed of abiocompatible, elastic material, preferably metallic. For example, theelastic wireform 106 may be formed of stainless-steel, titanium, orElgiloy. Alternatively, the elastic wireform 106 may be formed from abiocompatible polymer, such as Delrin or polyacetyl. In this sense,therefore, the term “wire” in wireform should not be construed aslimiting the material to metallic.

FIG. 7 illustrates an assembled valve 100 with the fabric skirt 110shown in FIG. 6 removed for clarity. That is, the fabric skirt 119 issized to drape outside of and surround the tissue-engaging base 104, butis removed in FIG. 7 to show the connection details between the base andthe leaflet subassembly 102. The valve 100 defines an inflow end 120 andan outflow end 122.

FIG. 9 illustrates an exemplary leaflet 108 having an arcuate cusp edge124 opposite a linear coapting edge 126. The cusp edge 124 is generallysemi-circular, and terminates at commissure portions 128. A pair ofoppositely-directed tabs 130 extend outward from both ends of thecoapting edge 126, and are seen in FIG. 6 prior to attachment to thewireform 106. That is, the tabs 130 from adjacent leaflets 108 jointogether and pass through the inverted U-shaped commissures 112 of theelastic wireform 106. In a preferred embodiment, each leaflet 108 isformed from pericardial tissue, such as bovine or equine pericardium, ora synthetic material, that has been suitably treated to render itbiocompatible.

With reference again to FIG. 6, the cusp edge 124 of each leaflet 108 isshaped so as to follow a cusp 114 of the elastic wireform 106. Thefabric skirt 110 extends to an inflow edge 132 from each of the cusps114, and when the skirt is assembled to the tissue-engaging base 104,the inflow edge extends substantially to the inflow end 120 (FIG. 7) ofthe valve. The fabric skirt 110 further terminates at outflow edges 134between adjacent wires of the wireform commissures 112, below theleaflet tabs 130 extending therethrough. The skirt 110 may be made of abiocompatible fabric such as polyester, or of other suitablebiocompatible sheet material.

The leaflet subassembly 102 attaches to the tissue-engaging base 104 atdiscrete locations, securely coupling each of the commissures 112 andcusps 114 of the elastic wireform 106 to the base. As seen best in FIG.6, the tissue-engaging base 104 comprises a tubularplastically-expandable member 140 having an inflow rim 142 and outflowrim 144. A plurality of commissure posts 146 are either rigidly attachedto, or securely coupled to, the tubular member 140 so as to extendgenerally axially beyond the outflow rim 144 in the outflow direction.Likewise, a plurality of cusp posts 148 are rigidly attached to, orsecurely coupled to, the tubular member 140 so as to extend beyond theoutflow rim 144. Because the commissure posts 146 couple to the wireformcommissures 112, they are longer than the cusp posts 148 that couple tothe wireform cusps 114.

As illustrated, both the commissure posts 146 and cusp posts 148 extendthrough upper and lower sleeves 150 a, 150 b, respectively provided onthe exterior of the tubular member 140, and are desirably axiallysecured therein. It should be noted that this is only one of numerouspossible ways to rigidly couple upstanding posts to aplastically-expandable tubular member. However, the posts 146,148 aredesirably located on the outside of the tubular member 140 so as not tointerfere with a balloon for expanding the tubular member from theinside, nor to interfere with blood flowing through the valve. It shouldalso be noted that in a reverse configuration, the posts 146, 148 may beinitially attached to the wireform commissures 112 and cusps 114,respectively, as part of the leaflet subassembly 102 and subsequentlyconnected to mating structures (not shown) provided on thetissue-engaging base 104.

A plurality of connectors are provided for attaching the elasticwireform 106 to the posts 146, 148 of the tissue-engaging base 104. Inparticular, as seen in FIG. 6, each commissure post 146 provides a lowercommissure connector 160 thereon. Likewise, each cusp posts 148 providesa lower cusp connector 162. In the illustrate embodiment, the outflowend of each of the posts 146, 148 is bent 90° to face radially inwardand a groove formed therein defines the respective connectors 160,162.

FIGS. 9-11 illustrate the configuration of the connection between theleaflet subassembly 102 and tissue-engaging base 104 at the commissuresof the valve. With specific reference to FIG. 10, the lower commissureconnector 160 of the commissure post 146 mates with an upper commissureconnector 164 of an insert 166 (isolated in FIG. 8) secured to thewireform is commissure 112. As seen in FIG. 11, adjacent leaflets 130extend radially outward between spaced wires of the wireform 106 andwrap around the insert 166 to be connected on an outer side thereof witha plurality of stitches 168. FIG. 8 illustrates one form of the insert166 wherein the upper commissure connector 164 comprises a downwardlyopening partial circle which mates with the groove of the lowercommissure connector 160, as seen in FIG. 10. In this manner, thecommissures 112 are securely fastened with respect to thetissue-engaging base 104 by virtue of the interaction between the lowercommissure connector 160 and upper commissure connector 164.

With reference again to FIGS. 6 and 7, a plurality of upper cuspconnectors 170 attach to the approximate midpoint of each of the cusps114 of the wireform 106. Each upper cusp connectors 170 is configuredand positioned to mate with the lower cusp connector 162 formed on eachof the cusp posts 140. Again, the upper cusp connector 170 may beprovided with a downwardly opening partial circle that mates with thegroove of the lower cusp connector 162.

With specific reference to FIG. 12, certain constructional details ofthe valve cusps are further illustrated. The fabric covering 116 of thewireform 106 is shown as a tube having an upper fabric extension 180 anda lower fabric extension 182 sandwiched around a radial portion 184 ofthe upper cusp connector 170. The upper cusp connector 170 extendsoutward and bends 90° downward to mate with the lower cusp connector162. The upper fabric extension 180 continues outward and downward inthe fabric skirt 110. The lower fabric extension 182 bends 180°underneath the cusp edge 124 of the respective leaflet 108. Stitching186 secures the combined layers of the upper extension 180, radialportion 184, first part of the lower extension 182, leaflet cusp 124,and wrapped-around portion of the lower extension 182.

Desirably, both the insert 166 and upper cusp connector 170 are madefrom a suture-permeable material having sufficient strength to maintainthe connections between the leaflet subassembly 102 and tissue-engagingbase 104. For example, the insert 166 and connector 170 may be made ofDelrin, or other suitable polymer. As illustrated, each of theconnectors 164 and 170 are partial circles that fit around tubulargrooves in the respective posts 146,148. Of course, other arrangementsare possible, and the present invention should not be considered limitedto those connectors illustrated.

As with the earlier embodiment, the valve 100 utilizes a low-stressconnection between the leaflets 108 and the elastic wireform 106. Inparticular, as seen in FIG. 11, the provision of the insert 166 providesa clamping force during diastole between the insert and the wireform 106against the portion of the leaflets 108 therebetween. The stitching 168is not subjected to direct tensile stresses, and there is thus lesschance for tearing.

Leaflet subassembly 102 is desirably stored in its expanded state, asseen in FIG. 6 (which, as mentioned, does not illustrate the commissureattachment structure). That is, the wireform 106 and leaflets 108 may bestored immersed in a preservative such as glutaraldehyde in a sterilecontainer until needed. In this regard, the prosthetic leaflets 108remain in their functional shape during storage. This greatly reducesadverse wrinkling or other permanent or semi-permanent damage to theleaflets over time, and improves the quality of the valve 100. At thesame time, the base 104 desirably does not include any bioprosthetic orotherwise perishable components, and thus may be stored in a separatedry sterile container. This method also permits the combination ofdifferent bases with any one leaflet subassembly 102, or visa versa. Forexample, the type of attachment mechanism (i.e., staples, barbs,sutures, etc.) of the base 104 to the annulus may be selected by thesurgeon, with different bases being attached in different ways, and allbeing combinable with a particular leaflet subassembly 102. Also, thetype of base may be selected based on patient indications; with aself-expanding base being preferred in some situations and aballoon-expanded base in others.

In use, the leaflet subassembly 102 is compressed from its expandedconfiguration to a size corresponding to the tissue-engaging base 104 inits compressed state (not shown). If the tissue-engaging base 104 isplastically deformable then it is initially supplied in its compressedstate. Alternatively, a self-expandable base 104 will have to becompressed either before or after connection to the similarly configuredleaflet subassembly 102. Compression of the leaflet subassembly 102 (andbase if necessary) may be accomplished using a tapered mandrel throughwhich the subassembly is passed, or with a cinch or other directconstricting means. The two components are then connected together, justprior to insertion into the patient's body, and the valve 100 deliveredsimultaneously to the host annulus site. To connect the two components,the fabric skirt 110 is passed around the outside of the commissureposts 146 and around the tubular member 140. Each of the upperconnectors 164 and 170 are caused to mate with the lower connectors 160,162. In the illustrated embodiment, such a mating operation simplyrequires forcing each of the partial circles defining the upperconnectors over the grooves defining the lower connectors. The partialcircles open slightly, but then spring inward when the connectors snaptogether and the groove is fully seated.

There are a number of ways to deliver the valve 100 to the aorticannulus. For one, the tubular member 140 may be mounted around a ballooncatheter and inserted via an introducer or other cannula into thepatient's vasculature and to the aorta. Alternatively, an open-heartprocedure or less-invasive port procedure may be utilized, with thetissue-engaging base 104 being delivered to the host annulus using aholder or other such means.

FIG. 16A depicts a sectional view of a heart 200 having a left ventriclechamber 202 opening to an ascending aorta 204 through an aortic annulus206. The ascending aorta 204 continues over an aortic arch 208, andbranches off into several upper body arteries 210 before descending tothe abdominal aorta (not shown). As mentioned above, the expandablevalves of the present invention can be delivered into proximity of theaortic annulus 206 in several ways, including through the patient'svasculature as shown.

In particular, a valve delivery catheter 212 is shown in the cutawayportion of the ascending aorta 204, having been introduced along thedirection of the arrow 214 so that a distal end thereof lies adjacentthe aortic annulus 206. The catheter 212 can be introducedpercutaneously into the patient's arterial system (e.g. into aperipheral artery such as the fermeral artery) and advanced to theascending aorta 204. The catheter shaft preferably has a length of atleast about 80 cm, usually about 90-100 cm, to allow transluminalpositioning of the shaft from the femoral and iliac arteries to theascending aorta. Alternatively, the shaft may have a shorter length,e.g. 20-60 cm, for introduction through the iliac artery, through thebrachial artery, through the carotid or subclavian arteries, or througha penetration in the aorta itself. In the femoral approach, the catheteris long enough and flexible enough to traverse the path through thefemoral artery, iliac artery, descending aorta and aortic arch. At thesame time, the catheter has sufficient pushability to be advanced to theascending aorta by pushing on the proximal end, and has sufficientaxial, bending, and torsional stiffness to allow the physician tocontrol the position of the distal end, even when the catheter is in atortuous vascular structure. Alternatively, the catheter 212 may bepassed through a port between ribs in the patient's thorax above theheart and through an incision in the aortic arch 208, in a so-calledminimally-invasive procedure.

Techniques for introducing catheters into the human vasculature arewell-known, and typically involve the introduction of a guidewire 216first, followed by an obturator or dilator (not shown) within a sheath218. The dilator facilitates introduction of the catheter sheath 218into the vasculature, and is then removed, though the guidewire 216typically remains in place. Subsequently, a valve of the presentinvention, such as valve 100 seen in FIGS. 6-15, is delivered over theguidewire 216 and to the distal end of the sheath 218. In accordancewith one aspect of the present invention, the valve 100 includes aballoon-expandable portion and thus is mounted over an expansion balloon222. To facilitate passage of the valve 100 through the sheath 218, apusher 224 may be used.

FIG. 16B illustrates a second step in the exemplary valve deliveryprocedure in which the sheath 218 is retracted in a proximal directionas indicated by arrow 226. Retraction of the sheath 218 exposes thevalve 100, which is positioned within the aortic annulus 206 with theassistance of fluoroscopy and radiopaque markers, ultrasonic imaging, orthe like. If the valve 100 includes self-expanding components,retraction of the sheath 218 releases the outer restraint on the valveand permits it to expand into contact with the annulus 206. In theillustrated embodiment, however, the tubular member 140 of thetissue-engaging base 104 is plastically-deformable and retains itsradially constricted configuration after retraction of the sheath 218.Because of the rigid connections between the leaflet subassembly 102 andthe base 104, the subassembly also remains in its constrictedconfiguration.

Finally, in FIG. 16C, the balloon 222 is inflated to cause thetissue-engaging base 104 to radially expand into contact with the aorticannulus 206, as indicated by the arrows 230. Simultaneously, the leafletsubassembly 102 radially expands by virtue of the rigid connection withthe base 104, and by virtue of its spring bias. A balloon inflationcatheter 232 is seen projecting from the pusher 224 and through theleaflet subassembly 102. With reference back to FIG. 6, the fabric skirt110 is captured between the tubular member 140 and the surroundingtissue, and is in direct contact therewith. Therefore, by virtue of thecontinuous connection between the cusp edges 124 of the leaflets 108 andthe fabric skirt 110, the skirt forms a flow channel for blood enteringthe inflow end 120 of the valve 100. Again, the plastically-expandabletubular member 140 may be slightly over-expanded to account for anyspring-back in the material. Further, as mentioned above, the tubularmember 140 may include staples or barbs or other such attachmentstructure for securely locating the valve 100 within the annulus 206.

Once the valve 100 is fully expanded and securely attached to theannulus 206, the balloon 222 is deflated and removed. Such an operationmay include elongating the balloon 222 in the distal direction andreducing its radial dimension by, for example, twisting. Care must betaken so as not to damage the leaflets within the subassembly 102 duringretraction of the balloon 222 therethrough. After the balloon 222 hasbeen retracted within the sheath 218, the entire catheter 212 is removedfrom the patient.

The fully formed valve 100 has a number of distinct advantages overprior expandable valves. For example, as mentioned above, the prostheticleaflets 108 may be stored in the final, uncompressed implantationshape. This is in contrast to prior expandable valves where the entirevalve may be initially compressed such that the leaflets are stored in acompressed state. Consequently, valves of the prior art can be storedfor years prior to use, and permanent wrinkling of the compressedleaflets may be a real problem.

Furthermore, each of the leaflets 108 is supported substantiallyentirely around the undulating wireform 106, which has proven to provideoptimal valve performance. Also, separate leaflets are used as opposedto a continuous tube, as in the first embodiment. Additionally, theadvantageous low-stress attachment structure of the leaflet tabs 130 tothe wireform commissures 112 further increases the durability of thevalve.

While the foregoing is a complete description of the preferredembodiments of the invention, various alternatives, modifications, andequivalents may be used. Moreover, it will be obvious that certain othermodifications may be practiced within the scope of the appended claims.

What is claimed is:
 1. A prosthetic heart valve, comprising: a supportstent including a tubular base along an inflow end and a plurality ofgenerally axially-extending commissure posts disposed evenly around thetubular base on an outflow end thereof, each commissure post having anaxial slot, wherein the base is plastically-expandable from a first sizeadapted for minimally invasive delivery, to a second, functional sizethat fits within a heart valve annulus; and a flexible tubular memberhaving a prosthetic section attached to the commissure posts so as todefine a plurality of prosthetic valve leaflets between the posts, and afabric section connected to the base, and wherein the tubular member isprimarily located within the posts except for a plurality of loops thatextend outward through each slot on each post, and further including aplurality of inserts sized lager than the slots, each of which insert iscaptured within a loop extending outward through each slot to retain theloop through the slot.
 2. The heart valve of claim 1, wherein theprosthetic section and fabric section are both generally tubular andattached together at a seam.
 3. The heart valve of claim 2, wherein theseam is spaced from the outflow end of the tubular base so that only thefabric section of the flexible tubular member contacts the tubular base.4. The heart valve of claim 2, wherein the seam is other than circular.5. The heart valve of claim 1, wherein the fabric section of theflexible tubular member attaches along a seam to the outflow end of thetubular base.
 6. The heart valve of claim 1, wherein the prostheticsection of the flexible tubular member is pericardial tissue.
 7. Theheart valve of claim 1, wherein the commissure posts are integrallyformed with the base, the base and commissure posts being initiallyformed from a flat section of material, wherein the commissure postsinitially extend from the inflow end of the base and are bent 180° toextend alongside the base and project beyond the base at the outflow endthereof.
 8. The heart valve of claim 7, wherein the fabric section ofthe flexible tubular member extends around the exterior of the tubularbase and within spaces created between each of the commissure posts andthe tubular base.
 9. The heart valve of claim 1, wherein the commissureposts each comprise: a first axial section extending from the inflow endof the base and spaced radially therefrom; a second axial sectiondefining the outflow extent of the post and a portion of the axial slot,the second section being radially inwardly offset from the firstsection; and a transition region between the first and second sections,wherein an enlarged portion of the axial slot is defined in thetransition region.
 10. The heart valve of claim 1, further including aplurality of stitches securing each loop of the flexible tubular memberto the corresponding insert.
 11. The heart valve of claim 10, furtherincluding stitching securing each insert to the corresponding commissurepost of the base.
 12. A prosthetic heart valve, comprising: a supportstent including a tubular base along an inflow end and a plurality ofgenerally axially-extending commissure posts each having an axial slotand being disposed evenly around the tubular base on an outflow endthereof; and a flexible tubular member having an outflow edge, whereinthe tubular member is primarily located within the posts except for aplurality of loops that extend outward through each slot on each post,and further including a plurality of inserts sized larger than theslots, each of which insert is captured within a loop extending outwardthrough each slot to retain the loop through the slot, the outflow edgeof the tubular member defining a plurality of valve leaflets.
 13. Theheart valve of claim 12, wherein the tubular base isplastically-expandable from a first size adapted for minimally invasivedelivery, to a second, functional size that fits within a heart valveannulus.
 14. The heart valve of claim 12, wherein the commissure postsare integrally formed with the base, the base and commissure posts beinginitially formed from a flat section of material, wherein the commissureposts initially extend from the inflow end of the base and are bent 180degrees to extend alongside the base and project beyond the base at theoutflow end thereof.
 15. The heart valve of claim 12, wherein theflexible tubular member has a prosthetic section attached to thecommissure posts and a fabric section connected to the base at a seam.16. The heart valve of claim 15, wherein the seam is other thancircular.
 17. The heart valve of claim 15, wherein the fabric section ofthe flexible tubular member extends around the exterior of the tubularbase and attaches along a seam to the outflow end of the tubular base.18. The heart valve of claim 15, wherein the prosthetic section of theflexible tubular member is pericardial tissue.
 19. The heart valve ofclaim 12, further including a plurality of stitches securing each loopof the flexible tubular member to the corresponding insert.
 20. Theheart valve of claim 19, further including stitching securing eachinsert to the corresponding commissure post of the base.